Shock absorber



Feb. 21?, 1937. C R, HANNA 171,831

SHOCK ABSORBER Original Filed Aug. 6, 1952 4 Sheets-Sheet l INVENTOR7mm/2 fr. Harz/7a.

` AToRNEY Feb. 23, 1937.? c. R.HANNA 2,071,831

SHOCK ABsoRBER Original Filed VAug. 6, 1932 4 Sheets-Sheet 2 WITNESSES:INVENTOR 6727220/2 R Hanna.

` ATTORNEY l Feb. 23, 1937. R HANNA 2,071,831

SHOCK ABSORBER original Fild Aug. 6,' 1932 4 sheets-sheet s 67/72/0/2 /Efifa/m@ cnw/2g Mei/y ATTORNEYy Feb. 23, 1937. c. R, HANNA 2,071,831

sHoc'K ABsoRBER Original Filed Aug. 6, 1932 4 Sheets-Sheet 4 Fgg 9.

Vr Vf "Vw "Mr ATTRNEY Patented Feb. 23, l1937 UNITED sTA'rEs VPMI-:NTori-"lele:

Clinton R. Westinghouse Hanna, Pittsburgh, Pa., assignor to Electric &Manuf acturing Company, East Pittsburgh, Pa., a corporation ofPennsylvania Original application August 6, 1932, Serial No.

6 claims. (C1. '10s-s2) relates to shock absorbers for railway vehicles,and more vices to prevent the shocks and undesirable ridvscription,

, a shock absorber that shall ing characteristics caused by the nosinghabit of railway vehicles, in short, my invention relates to devicesadapted to prevent nosing.

This invention constitutes a part divided out of, my applicationentitled Shock absorbers, filed on August 6, 1932, Serial No. 627,758.

In the following description. Amy shock absorber Will be described inconnection with a locomotive. However, it is to be understood that myshock absorber may be employed in connection with other vehiclesoperating on rails. In this dethe vehicle may be considered as havingtwo main parts, which may, in the interest of clarity, be convenientlyreferred to as the sprung and the unsprung masses.

The sprung mass comprises that part of the vehicle which is supported bythe springs, and the unsprung mass comprises the axle and wheels and anyother parts that may be mounted thereon.

An object of my invention is the provision of be reliable, compact, andefficient in operation, and shall be readily manufactured and installed.

Another object of my invention is the provision of shock absorberswhich, when mounted, up'on a locomotive or other rolling stock operatingo n rails, resist lateral oscillations of the unsprung mass of thelocomotive, and thereby prevent the nosing action of the locomotive.

Another object of my invention is the provision of shock absorberswhich, when mounted upon a locomotive or other rolling stock operating`on rails, allow thel free movement of the Iwheels.

and which in nol manner interfere with the spring equalizing system uponwhich the sprung mass of the locomotive is carried.

A still further object of my `invention is the provision for controllingthe operations of -ashock absorber by means of a control mass having two`degrees of freedom. Y

Other objects anda fuller understandingaof" speed of the locomotive;

Fig'. 3 is a vector diagram illustrating the phase relationbetween therotational movements of the center line of the locomotive about thecenter of rotation and the lateral motion of the center of rotation;

Fig. 4 diagrammatically illustrates a two-Wheel locomotive rotatingabout the center of rotation;

Fig. 5 graphically illustrates the sinusoidal movement of the lateraloscillations of the-unsprung mass of a locomotive moving longitudinallyalong the rails;

Fig, 6 is a diagrammatic end view of a locomotive .or other rollingstock and illustrates in addition the mounting of my shock absorbersbetween the sprung and the unsprung masses;

Fig. 7 is a graphical representation of the tracking characteristics ofa. locomotive; 1

Fig.y 8 illustrates the damped lateral oscillations of a locomotiverunning below the critical Fig. 9 represents the damped lateraloscillations of a locomotive provided with a shock absorber runningbelowthe critical speedof the -locomotive;

Fig. 10 illustrates the undamped and sustainedI lateral oscillations ofthe unsprung mass-of the locomotive without a shock absorber runningabove the critical speed of the locomotive;

Fig. v11 illustrates a damped lateral oscillation of a locomotiveprovided with a shock absorber running at the "critical speed of lthelocomotive; and,

Fig. l2.represents the lateral oscillations of the sprung mass of alocomotive provided with a shock absorberrunning above the criticalspeed" -ofma locomotive, wherein the amplitude of the lateral`oscillations is not totally damped, but

my invention 'may be had. by referring to the I following speciiicationtaken in connection with the accompanying drawings, inwhich:

Figure'l is 'a perspective cross sectional view of my shock absorber,the driving crank being shown by dot and dash lines; i

Fig. 2 is a side elevational electric locomotive having mounted thereonto resist the of the unsprung mass;

shock absorbers 'View of part ofi-an lateral oscillationsv `are stableat some predetermined low value.

Referring particularly to Fig. l of the drawings, my shock absorber.comprises, in general, a cylinder 2li which is adapted., to be mountedon the sprung mass of the locomotivea two-Way piston 2l having, asshown, theight end hollowed out to` receive a valve assemblyblock 6 6,and lhaving the left end hollowed out toreceivea control mass M, twomultiplying valves mounted withinV the valve assembly block tt, aplurality of fluid passages andassociated ball and check valves, a rockshaft 23, which, together withra trunnionv 26" and an arm 25, actuatesthe'two-way'piston 2i Within the cylinder 2t upon the relativehmovementsof the Sprung and theA unsprungmassesof thelocomotive. I n I y ,V

As best shown in Fig. 1, the cylinder housing to form a shoulder 42 forthe purpose of providing a relatively long bearing surface for therockshaft 23. As illustrated, the shoulder 42 is re Vcessed to receivepacking material 43 which may be securely held in place by means of aretaining washer 44. The washer and packing prevent leakage of theliquid fromv the housing 2li.

-The depending arm 25 operates in a space alongv the side of the two-Waypiston 2l. The piston 2| may thus be caused to move in the cylinder 2U.

As illustrated, the two-way piston 2l is, of course, shorter than thebore of the cylinder 20. Accordingly, this construction provideschambers 65 and 66 on opposite ends of the two-way piston 2 I forsubjecting a fluid contained therein to pressure to resistthe relativemovements of the sprung and the unsprung masses of the vehicle. Thecylinder 20, at the extreme ends of the bore,'is somewhat enlarged at 31to facilitate the machining of the bore of the piston.

For controlling the movement of a fluid through the uid passages in thevalve assembly block, two multiplying Valves, as V1 are mounted in theblock 64, which block is mounted in the hollowed out portion of thepiston 2 I. The piston is provided with suitable conduits to permit theflow of uid from the compression chamber past the valves controlled bythe mass M.

'I'he mass M is mounted in a balanced position and operates two leverswhich control the multiplying valves. Lever I I5 is pivoted at I I8 andlever I I2, secured to the mass M, is pivoted at the point II'I on aU-shaped portion of the lever II5. The right-hand endsof Y the leverscontrol the multiplying valves. In view of the connection of the leversthe mass M controls the valves as a function of both the verticalacceleration of the sprung mass of the locomotive and the rate of changeof relative movement of the sprung and unsprung masses.

In Fig. 2, I show a part of an electric locomotive in combination with ashock absorber embodying the features of my invention. The cylinder 20of the shock absorber is bolted or otherwise suitably connected to thesuperstructure of the sprung mass of the locomotive. The axle arm 22 ofthe shock absorber is connected to a bracket |20 that is'attached to thejournal box of the unsprung mass of the locomotive. As is well known inthe art, the primary purpose of a spring equalization system is, in thecase of uneven track, to equally distribute the weight of the sprungmass of a locomotive upon the wheels, and thereby insure substantiallyuniform traction between each vdriving wheel and the rails. If it werenot for the spring equalization system, whichv allows the wheels to movefreely up-and-down, one or more of the main driving wheels would, atevery irregular place in the tracks, be lifted from the tracks.Therefore, it is obvious that for a shock absorber to be operative forlocomotive use, it must in no way interfere with the function of thespring equalization system.

However, as will appear later in the description, while the springequalization system allows the free movement of the wheels and `thusuniform traction between all the driving wheels and the tracks; yet theelasticity of the springs in combination with the sprung mass of thelocomotive is the primary causeof the "nosing action of a locomotive.The undesirable ."nosing actions, that 'is the lateral oscillations ofthe unsprung mass of a locomotive, which is closely accompanied with therolling action of the sprung mass of the locomotive, is the principalfactor or condition that limits the safe maximum running speed of alocomotive.

My shock absorber, when mounted on a locomotive, provides for greatlyreducing the "nosing action of the unsprung mass of the locomotive, aswell as for causing no interference with the spring equalization system.

In considering the tracking characteristics of a locomotive, let usassume first that the locomotive is moving along a straight track. Ifsome transient disturbance, such, for example, as a crooked place in thetrack, causes the center line of the locomotive to assume an angularposition relative to the center line of the track, the locomotive willtravel in the direction of its own center. The angular position of thecenterv line of the locomotive relative to the center line of the track,together with the forward (or backward) longitudinal movement of thelocomotive, causes the locomotive to run across the track until theflanges of the leading wheels strike the rail. The impact of the flangesstriking the rail turns the locomotive and thus causes the locomotive torun back to the other side of the track. This lateral motion of thewheels running from one side across to the other is called nosing of theunsprung mass of a locomotive. Therefore, it is noted, from theforegoing, that the nosing action comprises essentially two mainmotions:

(l) A rotational movement about a vertical axis through some point inthe center line of the locomotive, which rotational movement, whensuperposed on the forward longitudinal motion of the locomotive,produces (2) a lateral motion of the said point about which the rotationtakes place. This point will hereinafter be referred to as the center ofrotation of the locomotive. It should be note-d, however, that this useor denotation of the term differs somewhat from the conventionaldenotation of the term because, according to its conventional use, thecenter of rotation is the point on a rotating body which has fio lateralmotion. For a locomotive, the center of rotation has no lateral motionresulting from the rotational movements of the locomotive but it doeshave lateral motion resulting from the forward longitudinal movement ofthe locomotive. Therefore, from the foregoing, it is observed that ifthe center line of the locomotive is not allowed to assume an angularposition with respect to the i center line of the track, the undesirablenosing action can not exist. As will later appear in the description, myshock absorber functions to prevent the center line of the locomotivefrom as.- suming an angular position relative to the center line of thetrack.

The phenomenon of nosing may best be understood by assigning symbols tothe various conditions affecting nosing" action and expressing theirrelationship mathematically.

a=the variable angle between the center line of the locomotive and thecenter line of the track.

A=the maximum value of a" during a cycle of the lateral oscillation ofthe unsprung mass of the locomotive.

V=the longitudinal velocity ofthe locomotive.

j=the frequency of the lateral oscillation.

y=lateral displacement of the center of rotation.

a==A cosine wt substantially equal to the value of the angle in radians,the lateral displacement of the center of rotationmay be expressed asfollows:

y= It Va cVIt=VA cosine vvtdt=yvv4sine wt (1)v .Vian-''- From Equations(l) -and (2), it is noted that: (l) The lateral motion ofthe center ofrotation is. about 90 out o f phase with the angular rotation about thecenter (2) The amplitude of the lateral motion of the center of rotationis Therefore, to describe the lateral motion of any point on the centerline of the locomotive, the motion resulting from the rotation of thecenter line must be added vectorially to the lateral translation of thecenter of rotation. For example, suppose that a two axle locomotive isrotating about a point midway between the axles (see the diagrammaticview in Fig. 4) and that, at the same time, the locomotive ismovinglongitudinally along the tracks. By letting :1:1 and :te bethelongitudinal distances between the cen- 5 ter of rotation and thefront and rear axles, re-

spectively, then :mA and .'czA equal the lateral movement of the frontand rear axles resulting from the rotational movement of the locomotiveabout -the center of rotation. From Equation (l) m it is noted, however,that the lateral motion of the axles resulting from the rotation, is 90out of phase with the lateral motion resulting from the longitudinalmovement of the locomotives. This vector condition is shown vectoriallyin Fig. 4. Also, the vector condition of one axle only is showngraphically in Fig. 5. l

The amplitude I of the resultant curve of Fig. 5, or length of the y 2VAC w cosine 0 L (3) Thus:

Cw cosine A---' 2V. I (4) Therefore, other quantities remainingconstant,

Equation (4) shows that the angularity A decreases as the speed of thelocomotive increases. Accordingly, for very high speeds, the resultantof the sine for small angles is dom;

tween the threads of the wheels and the rails,

which causes the locomotive to travel in the direction of its own centerline rather than in the direction line of the track. Hence, the maximumvalue of this disturbing force F is the weight of the locomotive timesthe coefficient of friction betweenlthe threads of the wheels and therails. The distance through which this force acts is Zymax, being thedistance through which the center of rotation moves in its lateraloscillation, -(see Fig. 5). The direction of this disturbing force F isdetermined by the motion itself. Therefore, the frequencies of thedisturbing force and the motion is always equal. if there is somenatural frequency at which the locomotive tends to oscillate, thenatural fre- ,quency and the disturbing force will always be inresonance.

Inasmuch as the weight of the sprung mass is so much heavier than theunsprung mass of a locomotive, and inasmuch as the modulus of elasticityR of the rails is large compared to the modulus of elasticity K of thesprings that support the sprung mass of the locomotive, the naturalfrequency of the locomotive is determined primarily by the combinationof the sprung mass and the elasticity of the springs that support thesprung mass (see Fig. 6) Strictly speaking, this is an elastic systemand, hence has two natural frequencies. Actually the stiffness of therails is so much greater than the springs of the locomotive that theeffect of the rails may be neglected.

As hereinbefore mentioned, by reason of the angularity A, between thecenter line of the locomotive and the center line of the track, thewheels run from one rail towards the other and back` again. Theselateral oscillations of the unsprung mass cause a corresponding' lateraloscillation to be imparted .to the sprung mass of the locomotive.However, by virtue of the spring that supports the sprung mass, thelateral oscillations of the sprung `mass takes the form of a rollingaction. That is to say, the sprung mass is displaced laterally while, atthe same time, the springs on one side of the locomotive are deectedupwardly and the springs on the other side are defiected downwardly. The.total inertia force P caused by the lateral accelerations of the sprungmass, may be consideredl,.as applied at the center of gravity (see Fig.6). The inertia In other words,

having two degrees of freeforce P applied at the center of gravity maybe replaced by a lateral force P' of equal magnitude,

i applied at the axle and two equal and opposite crease in thefrictional disturbing force F which,

in turn causes an increase in the rolling action oscillatory actionunless impeded by a resisting force, continues to build up to dangerousproportions, which, in cases of high speeds, becomes great enough tocause the lateral force P to spreag the rails and thus cause derailmentsand wrec of the sprung mass and the accompanying in- -crease in theinertia force P. This circuitous Accordingly the phenomenon of "nosingmay be characterized as self induced vibrations; that is to say, thedisturbing force F furnishing the energy to the vibrations is controlledby the motion itself, in contradistinction to force vibrations where thedisturbing force is independentof the motion. In Fig. 5, the maximumvalue of the disturbing force is represented by the line F being inphase with the curve a-:A cosine 'wt Therefore, by letting Q equal thewheel loading; n the number of axles, and f the coefficient of friction,the disturbing force F equals 2nfQ. The energy input during one cycle(four quartercycles) is 2nfQ times 4ymax.

Substituting the value of for ymx the energy input tending to causenosing becomes:

Input From Fig. 12, o,

Substituting (6) in (4), the expression for A becomes: n

Cw V2 CW FW ,2W2+v2-,/X ,2w2+v2 7) Substituting (7) in (5), theexpression for energy input for each cycle tending to cause nosingbecomes:

Input JX-12m n (8) The energy losses, which tend to minimize the nosingactions are mostly caused by the transverse sliding of the wheelsuponthe rails, as the locomotive oscillates about the center of rotation.The force of resistance at each Wheel is fQ; and,

7 from Fig. 4, the sliding distance through which this force acts is xlAand zA for the front and rear wheels, respectively. The sliding distancemay also be expressed as follows:

For a locomotive with any number of axles, Equation (9) may be generallyexpressed as follOWSI 1 2 Energy loss: 8AfQZ\/X2+ (10) n Substituting(7) in (10) the final equation for energy loss is as follows:

I Therefore, the energy available to sustain and build up theoscillations may be obtained by subtracting Equation (11) from Equation(8). Thus:

If the value of V is less than the right hand side of the Expression(13), the net energy is negative; and therefore, any lateraloscillations of the unsprung mass of a locomotive that starts will bequickly damped out. Conversely, when the value of AV1 is greater thanthe righiI hand side of the Expression (13), energy is available -tosustain and increase any lateral oscillations of the unsprung mass of alocomotive that starts. Therefore, the value of V given in Equation 13may be considered as a critical speed below which lateral oscillationsof the unsprung mass of a locomotive cannot occur, and above whichlateral oscillations can occur. This condition is shown graphically byvrcurves I and II of Fig. 7. The frictional loss curve I drops while theenergy input curve II increases as the speed increases, for the reasonthat the angularity A, which determines the frictional loss, decreasesas the speed increases, and the lateral displacement gmx, whichdetermines the energy input increases as the speed increases. Thevertical line at 53 miles per hour represents the critical speed of thelocomotive. Forspeeds below the critical speed,

the frictional losses of the unsprung mass of the locomotive (see curveI) is greater than the energy input of the unsprung mass of thelocomotive (see curve II). Consequently, for speeds below the criticalspeed any lateral oscillations of the unsprung mass that start arequickly damped out. For speeds above the critical speed, the reversecondition is true, and thus energy is available to sustain the lateraloscillations of the sprung mass of the locomotive (see shaded portionbetween curves I and II).

However, by mounting shock absorbers, con- I structed in accordance withmy invention, between the sprung mass and the unsprung masssubstantially no energy is available to sustain the lateral oscillationsof the unsprung mass lof the locomotive.

My shock absorber, when mounted on a locomotive provides for resistingthe rolling action of the sprung mass, for the reason that thecontrol-mass M'is responsive to the vertical component of the rollingaction. Thus, under the condition represented in Fig. 6 the shockabsorber on the right side of the sprung mass resiststhe downwardcomponent-of` the rolling action and the shock absorber on the left sideresists the upward component of the rolling action. When the force Preverses, the opposite condition is true. This means that the magnitudeof the lateral force P applied at the center of gravity of the sprungmass is reduced to a very low value. This reduction in turn, causes thelateral force P', applied to the axle of the unsprung mass, to beaccordingly reduced to a very low value, with the result that theangularity A between the center line of the locomotive and locomotive,prevents the nosing action of theI locomotive for all speeds.

In Figs. 8 to 12, inclusive, eral oscillations of the unsprunglocomotive with and without a shock absorber. In all of these cases thetrackA is presumed to be straight and the magnitude of the rst lateraloscillation is the same. Fig. 8 represents the lateral oscillations ofthe unsprung mass of a locomotive without any shock absorber below thecritical speed. This lateral oscillation becomes damped, for the reasonthat the fric- I illustrate the latt tional losses of the unsprung massof the locoof the track, and thereby motive are greater thanv the energyinput of the unsprung mass.

. Fig. 9 represents the same condition as Fig. 8, except that thelocomotive is provided with shock absorbers. I n this case the lateraloscillations are damped somewhat quicker, since my shock absorbers addto the damping action caused by thev frictional losses of the unsprungmass.

The lateral oscillation represented by curve in Fig. 10 is for alocomotive having no shock absorber running above the critical speed. Inthis case energy is available to sustain the lateral oscillation of theunsprung mass, and as a result the amplitude builds up to largeproportions, thus causing corresponding large lateral forces on therails.

Fig. 1l represents the same condition as Fig. 12 except that thelocomotive is provided with a shock absorber in which the resistingforce of the shock absorber is suiiiciently large to totally damp thelateral oscillations of the unsprung mass of the locomotive to zero.

Fig. 12 representsV the same condition as Figs. 10 and 11 except thatthe locomotive is provided with a shock absorber in which the resistingforce of the shock absorber is not quite suilciently large to totallydamp out the lateral oscillations of the unsprung mass of thelocomotive. In case the amplitude of the lateral oscillations is readilydamped down to a very low value at which point age to the rolling stock,is totally avoided, even at speeds greatly in excess of miles an hour ormore. Another beneficial result is that the maintenance of the rails androad bed are materially reduced. If high speed locomotives are allowedto exert high lateral forces upon the rails, as a result of an undampednosing action, the rails, after they are used a short period becomeWarped, which, in turn, causes the nosing action to become worse. Thisaction is cumulative and in some cases the track, if lnot properlymaintained, becomes excessively crooked, takingI the form of This willbe a substantially sinusoidal path. greatly avoided by the action of myshock absorbers which keep the lateral forces of the unsprung mass to avery low minimum.

Therefore, I have disclosed a shock absorber mounted on a locomotive,which shock absorber provides for reducing the angularity between thecenter line of the locomotive 'and the center line materially reducesthe masses of al l. An inertia controlled shock absorber for arailvehicle connected between the sprung and unsprung masses of a railvehicle adapted to produce a resisting force to relative movements ofthe sprung and unsprung mass of a value deter- -mined by the rate ofchange of velocity of the sprung mass relative to the unsprung mass tothus reduce the nosing action of the vehicle.

2. In a rail vehicle having a sprung and an unsprung mass in which theunsprung mass of the vehicle is constrained toI travel on a track havinglimited lateral clearances, thus permitting the center line of thevehicle to assume an angularity with the center line of the track and inwhich the sprung mass of the vehicle, by reason ofthe angularity, iscaused to produce a tion and thereby increase the angularity, which, incombination, with the rolling action produces sustained lateraloscillations of the unsprung mass of the vehicle, an inertia shockabsorber connected between the sprung and unsprung masses of the railvehicle and that is thus responsive to the rolling action of the sprungmass of the vehicle to thus counteract such rolling action by a lforcedetermined by the rate of change of velocity of the sprung mass duringrolling to thus reduce the angularity and thus limit the amplitude ofthe lateral oscillations of the unsprung mass of the vehicle toy a lowvalue.

3. In a rail vehicle having. a sprung mass and an unsprung mass and inwhich, as is necessary for rail vehicles, the unsprung mass isconstrained to travel on a track having limited lateral clearance, incombination, an inertia controlled shock absorber comprising a memberconnected to the sprung mass, a second member connected tothe unsprungmass, and inertia controlled means adapted to vary the damping force ofthe shock absorber as a function of the relative movement of the sprungand unsprung masses of the vehicle, whereby the trackingcharacteristicsof the vehicle are improved.

4. In a rail vehicle having a sprung mass and an' unsprung mass and inwhich, as is necessary for rail vehicles, the unsprung mass isconstrained to travel on a track having limited lateral clearance, incombination, an inertia controlled shock absorber comprising a memberconnected to the sprung mass, a second member connected to the unsprungmass, inertia means mounte-d on the sprung mass and adapted to resistrelative movement of the sprung and unsprung masses as a function of themovement of the sprung mass whereby the tracking characteristics of thevvehicle are improved. i

5. In a rail vehicle having a sprung mass and an unsprung mass and inwhich, as is necessary for rail vehicles, the unsprung mass isAconstrained to travelon a track having limited lateral clearance, incombination, an inertia controlled shock absorber comprising a memberconnected to the sprung mass, a second member connected to the unsprungmass, inertia means operable by the upward vertical movement of thesprung mass to resist the relative movement of the sprung and unsprungmasses as a function of the rate of change. of upward vertical velocityof the sprung mass, whereby the tracking characteristics of the vehicleare improved.

rolling acan unsprung mass and in which, as is necessary i for railvehicles, the unsprung mass is constrained to travel on a track havinglimited lateral c1earance, in combination, an inertia controlled shockabsorber comprising a member connected to the sprung mass, a secondmember connected to the unsprung mass, inertia means operable by theupward vertical movement of the sprung mass and the relative movement ofthe sprung mass and unsprung mass when the unsprung mass is eithervertically stationary or moving vertically upwardly only, to thusimprove the tracking characteristics of the vehicle.

CLINTON R. HANNA.

